Brake regulating system for stabilizing the motion of a commercial vehicle

ABSTRACT

A brake regulating system ( 1, 1 ′) particularly suitable for stabilizing the motion of a commercial vehicle is described, in which a control unit ( 12 ) outputs, as a function of a number of input variables, a predefined manipulated variable for the brake pressure of each wheel ( 2, 4, 6, 8 ) of a commercial vehicle ( 10 ) and/or a predefined manipulated variable for an output variable of the drive engine. For detecting the input variables, the input of the control unit ( 12 ) is connected to a steering angle sensor ( 70 ) for detecting a steering angle predetermined by the driver, to a sensor system for determining the yaw rate of the commercial vehicle ( 10 ), and to a first acceleration sensor ( 76 ) for detecting the transverse acceleration of the commercial vehicle ( 10 ).

DESCRIPTION

[0001] The present invention relates to a brake regulating system for stabilizing the motion of a commercial vehicle in which, as a function of a number of input variables for each wheel of the commercial vehicle, a control unit predetermines a manipulated variable for its brake pressure and/or a manipulated variable for an output variable of the drive engine.

[0002] Within the scope of the vehicle dynamics regulation of a motor vehicle, a dynamic brake regulating system may be used for stabilizing the vehicle motion in which a targeted and selective brake intervention may be executed on each wheel by individually predetermining a brake pressure for each wheel. Such a brake regulating system for a passenger vehicle, as is known from German Patent Application 39 19 347 A1, includes a central control unit, which when needed, e.g., when instability of the driving condition begins or is already occurring, determines an individual brake pressure for each wheel from a number of specific input variables for the particular driving situation.

[0003] The control unit subsequently transmits a manipulated variable for the brake pressure of the particular wheel to a modulator assigned to that wheel; the modulator in turn acts on the brake system, which is normally a hydraulic brake system, setting the brake pressure, required for stabilizing the driving situation, at the particular wheel. In addition or alternatively to providing the manipulated variables for the brake pressures of the wheels, the control unit may also determine a manipulated variable for reducing an output variable of the vehicle drive, e.g., the engine torque, so that, via targeted reduction of the driving power, a stabilization of the driving situation may be effected or at least supported.

[0004] Measured data regarding the wheel speeds, the yaw rate of the vehicle, and the steering wheel angle representing the driver's intention, is supplied as input variables to the control unit of the brake regulating system known from German Patent Application 39 19 347 A1. A measured yaw rate of the vehicle corresponding to an actual state is then determined in the control unit from this data and compared to a desired yaw rate, corresponding to a setpoint state determined from the steering wheel angle. When needed, i.e., in the case of a discrepancy between actual state and setpoint state, manipulated variables for individual brake pressures of the wheels are determined from the degree of the discrepancy and passed on to the modulators assigned to the particular wheels.

[0005] In contrast to a passenger vehicle, a higher number of degrees of freedom of movement have to be taken into account in the vehicle dynamics regulation of commercial vehicles. Due to the comparatively higher center of gravity, tilting motions or rolling motions of the vehicle body may occur, for example. Therefore, for reliably stabilizing the vehicle motion when used in a commercial vehicle, the brake regulating system known from German Patent Application 39 19 347 A1 is only conditionally suitable.

[0006] Therefore, the object of the present invention is to provide a brake regulating system of the type mentioned above which is also particularly suitable for use in a commercial vehicle.

[0007] According to the present invention, this object is achieved in that the input of the control unit is connected to a steering angle sensor for detecting a steering wheel angle predetermined by the driver, to a sensor system for determining the yaw rate of the commercial vehicle and to a first acceleration sensor for detecting the transverse acceleration of the commercial vehicle.

[0008] The present invention is based on the consideration that, for use in a commercial vehicle, measured values characterizing the steering angle (and thus the driver's intention) and measured values characterizing the yaw rate of the commercial vehicle should also be supplied to the control unit of the brake regulating system as input variables in addition to the current wheel speed values. Moreover, to allow for the comparatively greater complexity of the handling properties of a commercial vehicle, the float angle, which should always be kept below the limit value characteristic for the breakaway of the commercial vehicle, should also be taken into account in the brake regulation. The float angle is a variable derivable from the yaw rate of the commercial vehicle and the transverse acceleration of the commercial vehicle acting at its center of gravity. The brake regulating system, designed for a particularly reliable usability in commercial vehicles, is thus also designed for supplying measured values to the control unit which are characteristic for the transverse acceleration of the commercial vehicle.

[0009] Advantageous embodiments of the present invention are the subject of the subclaims.

[0010] The sensor system appropriately includes a yaw rate sensor for determining the yaw rate of the commercial vehicle. The yaw rate sensor may be designed as a yaw rate gyro; however, it is preferably designed as a sensor according to the Coriolis principle. The sensor may be situated at any location on the commercial vehicle; however, it is preferably positioned directly at or close to the center of gravity of the commercial vehicle. Based upon the measured values supplied a_(y1) (=the transverse acceleration measured by the first acceleration sensor) and ω_(z) (=the measured yaw rate), the control unit determines the transverse acceleration a_(y) acting at the center of gravity of the commercial vehicle and necessary for determining the float angle according to the relation:

a _(y) =a _(y1)−ω*_(z) ·x ₁,

[0011] where ω*_(z) represents the yaw acceleration derived from measured yaw rate ω_(z) and x₁ represents the position of the acceleration sensor in relation to the center of gravity of the commercial vehicle, measured in the longitudinal direction of the commercial vehicle. x₁ assumes positive values in the forward direction and negative values in the reverse direction.

[0012] In an alternative advantageous design, the sensor system for determining the yaw rate of the commercial vehicle includes a second acceleration sensor for detecting the transverse acceleration of the commercial vehicle, the second acceleration sensor, viewed in the longitudinal direction of the commercial vehicle, being situated at an offset to the first acceleration sensor. In this system, which permits omitting the yaw rate sensor and is thus a particularly cost-effective design of the brake regulating system, the control unit determines the yaw rate of the commercial vehicle based upon the measured values supplied to it a_(y1) (=the transverse acceleration measured by the first acceleration sensor) and a_(y2) (=the transverse acceleration measured by the second acceleration sensor), according to the relation:

ω_(z)=∫(a _(y1) −a _(y2))/(x ₁ −x ₂)dt,

[0013] where x₁ and x₂ represent the positions of the first and second acceleration sensor in relation to the center of gravity of the commercial vehicle, each measured in the longitudinal direction of the commercial vehicle. x₁ and x₂ assume positive values in the forward direction and negative values in the reverse direction.

[0014] In this arrangement, the control unit of the brake regulating system determines transverse acceleration a_(y) acting at the center of gravity of the commercial vehicle according to the relation:

a _(y)=(a _(y1) ·x ₁ −a _(y2) ·x ₂)/(x ₁ −x ₂)

[0015] When equipping an articulated vehicle, formed by the commercial vehicle provided as the semitrailer tractor and a semitrailer connected thereto, with a brake regulating system, it must be pointed out that, compared to the commercial vehicle alone, the semitrailer unit has an additional degree of freedom, namely due to the articulation angle formed by the longitudinal axes of the semitrailer tractor and the semitrailer. With regard to the stability regulation it must also be pointed out that possible jackknifing of the semitrailer in relation to the semitrailer tractor may result in destabilization. In order to integrate this degree of freedom into the stability regulation, in an advantageous refinement, the input of the control unit of the brake regulating system is connected to a articulation angle sensor for detecting the articulation angle between the semitrailer tractor and the semitrailer connected thereto.

[0016] In an alternative advantageous refinement, the input of the control unit is connected to a second sensor system for determining the yaw rate of the semitrailer connected to the semitrailer tractor. The second sensor system in particular may also be designed as a yaw rate sensor according to the Coriolis principle. In this arrangement, the control unit determines the articulation angle from the values, supplied as input variables, for the yaw rate of the trailer ω_(za) and the yaw rate ω_(z) of the commercial vehicle according to the relation:

Ψ=∫(ω_(z)−ω_(za))dt

[0017] This concept is also extendable to truck trains or semitrailer trains, i.e., several trailers coupled behind the commercial vehicle used as the towing vehicle, each trailer being equipped with a sensor system for determining its yaw rate, and, from the yaw rates measured, the control unit determining the articulation angles between each two consecutive vehicles of the truck train.

[0018] Due to the raised center of gravity vis-a-vis a passenger car, it is of particular importance in the stability regulation of a commercial vehicle to take into account the tendency to tilt. This takes place here preferably by taking into account the vehicle tilt which is detected based upon the roll angle formed by a vehicle axis and a reference direction predetermined by the vehicle body. To achieve this, the input of the control unit is advantageously connected to a roll angle sensor for determining the roll angle of the commercial vehicle.

[0019] In an alternative advantageous design, the input of the control unit is connected to a roll velocity sensor for detecting the angular velocity between the vehicle body and a vehicle axis. The roll angle is calculatable in the control unit by integration of the measured angle speed over time.

[0020] The advantages, achieved through the present invention, are in particular that, by taking into account input variables for the control unit from which the transverse acceleration acting at the center of gravity of the commercial vehicle is derivable, the brake regulating system is particularly reliably applicable, even despite the comparatively complex stability regulation of a commercial vehicle. Due to the above-mentioned applications of additional sensors, which thus enable the supply of additional particularly suitable input parameters to the control unit, the brake regulating system is adaptable to the requirements specific to commercial vehicles in a simple manner.

[0021] An exemplary embodiment of the present invention is explained in greater detail based upon the drawing.

[0022]FIG. 1 schematically shows a brake regulating system for stabilizing the motion of a commercial vehicle,

[0023]FIG. 2 shows an alternative embodiment of the brake regulating system in FIG. 1,

[0024]FIG. 3 schematically shows a brake regulating system for stabilizing the motion of a tractor-trailer unit, formed of a commercial vehicle and a trailer coupled thereto, and

[0025]FIG. 4 shows an alternative embodiment of the brake regulating system in FIG. 3.

[0026] The same components are marked with the same reference numbers in all figures.

[0027] Brake regulating system 1, according to FIG. 1, is provided for the stability regulation of a commercial vehicle 10 depicted by its wheels 2, 4, 6, 8. Brake regulating system 1 includes a central control unit 12, which when needed, e.g., when instability of the driving condition begins or is already occurring, determines an individual brake pressure for each wheel 2, 4, 6, 8 from a number of specific input variables for the particular driving situation.

[0028] Commercial vehicle 10 is equipped with a pneumatic braking system including a compressed air tank 14. A service brake valve 17, operable by the driver of commercial vehicle 10 via a brake pedal 16, is assigned to the compressed air tank. Compressed air tank 14 supplies a pneumatic brake line system 18 with brake pressure as a function of a braking action exercised by the driver via brake pedal 16. Brake line system 18 includes a number of brake lines 20, 22, 24, 26 each of which is assigned to a wheel 2, 4, 6, and 8. Each brake line 20, 22, 24, 26 connects compressed air tank 14 to a pressure regulating module 28, 30, 32, and 34, each being situated upstream from wheels 2, 4, 6, 8, and each setting a brake pressure at the assigned wheel 2, 4, 6, and 8 as a function of the pedal position of brake pedal 16. In a case of emergency, i.e., of the failure of the control electronics, each brake line 20, 22, 24, 26 connects compressed air tank 14 to the particular pressure regulating module 28, 30, 32, and 34, even with an opened service brake valve 17, in such a way that braking of all wheels 2, 4, 6, 8 may take place. Moreover, brake regulating modules 28, 30, 32, 34 are also directly pneumatically connected to compressed air tank 14, i.e., bypassing service brake valve 17, thereby setting the brake pressure at each wheel 2, 4, 6, 8, required for a stabilization of the driving situation, even without a braking action by the driver. For this purpose, as a function of manipulated variables supplied, the modules convert the brake pressure predetermined by compressed air tank 14 into brake pressures individually predetermined for each wheel 2, 4, 6, 8 which are supplied to downstream lines 36, 38, 40, 42 which are connected to the brake system of the particular wheel 2, 4, 6, and 8.

[0029] The manipulated variable for the brake pressure of the particular wheel 2, 4, 6, 8 is predetermined by control unit 12. For this purpose, the output of the control unit 12 is connected to pressure regulating modules 28, 30, 32, 34, assigned to wheels 2, 4, 6, 8, via signal lines 44, 46, 48, 50. In addition or alternatively to providing the manipulated variables for the brake pressures of wheels 2, 4, 6, 8, control unit 12 may also determine a manipulated variable for reducing an output variable of the vehicle drive, e.g., the engine torque, so that, via targeted reduction of the driving power, a stabilization of the driving situation may be effected or at least supported.

[0030] The input of control unit 12 is connected to speed sensors 60, 62, 64, 66, assigned to wheels 2, 4, 6, 8, via signal lines 52, 54, 56, 58. The speed sensors determine measured values for the instantaneous speed of each wheel 2, 4, 6, 8 which are subsequently supplied to control unit 12 as input variables via signal lines 52, 54, 56, 58. In addition, the input of control unit 12 is connected to a steering angle sensor 70 via signal line 68 for detecting a steering angle. Steering angle sensor 70 determines a measured value characterizing the angle of steering wheel 72 predetermined by the driver and thus the driver's intention, which is suppliable to the control unit via signal line 68 as another input variable.

[0031] In addition, the input of control unit 12 is connected to a sensor system including a yaw rate sensor 74, designed according to the Coriolis principle, for determining the yaw rate of commercial vehicle 10, to a first acceleration sensor 76 for detecting the transverse acceleration of commercial vehicle 10, and to a roll angle sensor 78 for detecting the roll angle of commercial vehicle 10. In other words: the yaw rate, the transverse acceleration, and the roll angle of commercial vehicle 10 are suppliable to control unit 12 as additional input variables. These input variables together with the input variables generally used such as the wheel speeds, for example, are taken into account for determining the manipulated variables for the brake pressures at wheels 2, 4, 6, 8, so that brake regulating system 1 operates particularly reliably when used in commercial vehicle 10, despite the greater complexity of the motions.

[0032] In forming the manipulated variables for the brake pressures, control unit 12 takes into account in particular transverse acceleration a_(y) acting in the center of gravity of commercial vehicle 10. This is determined by control unit 12 from measured values supplied to it a_(y1) (=the transverse acceleration measured by acceleration sensor 76) and ω_(z) (=the yaw rate measured by yaw rate sensor 74) according to the relation:

a _(y) =a _(y1)−ω*_(z) ·x ₁,

[0033] where ω*_(z) represents the yaw acceleration derived from measured yaw rate ω_(z) and 1₁ represents the distance between acceleration sensor 76 and the center of gravity of the commercial vehicle, measured in the longitudinal direction of the commercial vehicle.

[0034] The transverse acceleration at the center of gravity of commercial vehicle 10 determined in this way is used together with the yaw rate for determining the float angle. Control unit 12 ensures here that a predetermined limit value for the float angle is not exceeded, thus preventing a breakaway of commercial vehicle 10.

[0035] Likewise, the roll angle detected by roll angle sensor 78 is monitored, so that an impending tilt of commercial vehicle 10 is detected early enough to introduce countermeasures. Instead of roll angle sensor 78, a roll velocity sensor for detecting the angular velocity between the vehicle body and a vehicle axis may also be provided alternatively. The roll angle may be calculated in control unit 12 by integration of the angular velocity measured over time.

[0036] In the exemplary embodiment according to FIG. 2, a second acceleration sensor 80 for detecting the transverse acceleration of commercial vehicle 10 is provided instead of yaw rate sensor 74, the input of control unit 12 being connected to the second acceleration sensor via signal line 81. Viewed in longitudinal direction 82 of commercial vehicle 10, second acceleration sensor 80 is situated at an offset to first acceleration sensor 76. In this exemplary embodiment, first acceleration sensor 76 together with second acceleration sensor 80 form the sensor system for determining the yaw rate of commercial vehicle 10.

[0037] In this system, which permits omitting yaw rate sensor 74, control unit 12 determines yaw rate ω_(z) of commercial vehicle 10 based upon the measured values supplied to it a_(y1) (=the transverse acceleration measured by first acceleration sensor 76) and a_(y2) (=the transverse acceleration measured by second acceleration sensor 80), according to the relation:

ω_(z)=∫(a _(y1) −a _(y2))/(x ₁ −x ₂)dt,

[0038] where x₁ and x₂ represent the distance between first and second acceleration sensor 76, 80 and the center of gravity of the commercial vehicle, each measured in longitudinal direction 82 of the commercial vehicle.

[0039] Control unit 12 of brake regulating system 1 determines transverse acceleration a_(y) acting in the center of gravity of commercial vehicle 10 according to the relation:

a _(y)=(a _(y1) ·x ₁ −a _(y2) ·x ₂)/(x ₁ −x ₂)

[0040] The same interim values are thus available for further processing in this embodiment as were in the preceding exemplary embodiment.

[0041] Brake regulating system 1′ according to FIG. 3 is designed for use in an articulated vehicle formed from a commercial vehicle 10, provided a a truck tractor, and a semitrailer, illustrated only by its longitudinal axis 84, coupled thereto. Articulation angle Ψ, formed by longitudinal direction 82 of commercial vehicle 10 and longitudinal axis 84 of the trailer, may also be of importance for the stability regulation of such an articulated vehicle or semitrailer truck. In particular, possible jackknifing of the semitrailer with respect to commercial vehicle 10 may result in destabilization. In order to integrate this degree of freedom into the stability regulation, the input of control unit 12 of brake regulating system 1′ is connected to a articulation angle sensor 88 for detecting articulation angle Ψ via signal line 86.

[0042] In the exemplary embodiment according to FIG. 4, the input of control unit 12 of brake regulating system 1′ is connected to yaw rate sensor 100, designed according to the Coriolis principle, for determining the yaw rate of the semitrailer connected to commercial vehicle 10. In this arrangement, control unit 12 determines articulation angle Ψ from the values, supplied as input variables, for the yaw rate of the semitrailer ω_(za) and the yaw rate ω_(z) of commercial vehicle 10 according to the relation:

Ψ=∫(ω_(z) −ω _(za))dt

[0043] Of course, the concept for determining the yaw rate according to the exemplary embodiment in FIG. 2, i.e., the use of a pair of acceleration sensors at an offset in the longitudinal direction instead of the yaw rate sensor, may also be applied to the exemplary embodiments according to FIGS. 3 and 4.

[0044] List of Reference Numbers

[0045]1, 1′ brake regulating system

[0046]2, 4, 6, 8 wheels

[0047]10 commercial vehicle

[0048]12 control unit

[0049]14 compressed air tank

[0050]16 brake pedal

[0051]17 service brake valve

[0052]18 brake line system

[0053]20, 22, 24, 26 brake lines

[0054]28, 30, 32, 34 pressure regulating modules

[0055]36, 38, 40, 42 lines

[0056]44, 46, 48, 50,

[0057]52, 54, 56, 58 signal lines

[0058]60, 62, 64, 66 speed sensors

[0059]68 signal line

[0060]70 steering angle sensor

[0061]72 steering wheel

[0062]74 yaw rate sensor

[0063]76 acceleration sensor

[0064]78 roll angle sensor

[0065]80 acceleration sensor

[0066]81 signal line

[0067]82 longitudinal direction

[0068]84 longitudinal axis

[0069]86 signal line

[0070]88 articulation angle sensor

[0071]100 yaw rate sensor

[0072] a_(y) transverse acceleration in the center of gravity

[0073] a_(y1), a_(y2) transverse acceleration measured

[0074] ω_(z) yaw rate

[0075] ω_(za) yaw rate of the trailer

[0076] ω*_(z) yaw acceleration

[0077] Ψ articulation angle 

What is claimed is:
 1. A brake regulating system (1, 1′) for stabilizing the motion of a commercial vehicle (10), in which a control unit (12) outputs, as a function of a number of input variables, a predefined manipulated variable for the brake pressure of each wheel (2, 4, 6, 8) of the commercial vehicle (10) and/or a predefined manipulated variable for an output variable of the drive engine, the input of the control unit being connected, for detecting the input variables, to a steering angle sensor (70) for detecting a steering angle predetermined by the driver, to a sensor system for determining the yaw rate of the commercial vehicle (10), and to a first acceleration sensor (76) for detecting the transverse acceleration of the commercial vehicle (10).
 2. The brake regulating system (1, 1′) as recited in claim 1, wherein its sensor system for determining the yaw rate of the commercial vehicle (10) includes a yaw rate sensor (74).
 3. The brake regulating system (1, 1′) as recited in claim 1, wherein its sensor system for determining the yaw rate of the commercial vehicle (10) includes a second acceleration sensor (80) for detecting the transverse acceleration of the commercial vehicle (10), the second acceleration sensor (80) being situated at an offset to the first acceleration sensor (76) viewed in the longitudinal direction (82) of the commercial vehicle (10).
 4. The brake regulating system (1, 1′) as recited in one of claims 1 through 3, wherein the input of the control unit (12) is connected to a articulation angle sensor (88) for detecting the articulation angle (ψ) between the longitudinal direction (82) of the commercial vehicle (10) and the longitudinal axis (84) of a trailer connected thereto.
 5. The brake regulating system (1, 1′) as recited in one of claims 1 through 3, wherein the input of the control unit (12) is connected to a second sensor system for determining the yaw rate of a trailer connected to the commercial vehicle (10).
 6. The brake regulating system (1, 1′) as recited in one of claims 1 through 5, wherein the input of the control unit (12) is connected to a roll angle sensor (78) for detecting the roll angle of the commercial vehicle (10).
 7. The brake regulating system (1, 1′) as recited in one of claims 1 through 5, wherein the input of the control unit (12) is connected to a roll velocity sensor (100) for detecting the angular velocity between the vehicle body and a vehicle axis. 